Electronic fuel injection control circuit

ABSTRACT

An electronic fuel injection system for automobile internal combustion engines includes a resonant circuit which is formed and whose capacitance is charged by a silicon-controlled rectifier triggered by the engine. The resulting half-sine wave voltages across the load resistance are of constant duration and are changed from a half-sine waveform to more triangular waves. Transistor circuits, at least one of which is biased by a voltage representing a number of engine operating conditions, convert the triangular waves into square wave voltages having a constant amplitude and a duration corresponding to the engine operating conditions. The resulting square waves or pulses are applied to solenoid injector valves to open them synchronously with the engine for required periods of time to supply the needed amounts of fuel.

United States Patent Richard Bert Beishir [54] ELECTRONIC FUEL INJECTION CONTROL CIRCUIT 6 Claims, 6 Drawing Figs.

52 11.5. CI 123 32 EA, 123/119, 123/139 E [51] Int. Cl ..F02m 51/00 [50] Field of Search 123/32, 32 E, 119, 139 13,148 E [56] References Cited UNITED STATES PATENTS 3,456,628 7/1969 Bassot et al 123/32 EA O O O S.C.R. VOLTAGE 2s 9 0 SOURCE.

30 H Ii Primary Examiner-Laurence M. Goodridge AttorneyEdward H. Casey 123/119X 123/32 EA ABSTRACT: An electronic fuel injection system for automobile internal combustion engines includes a resonant circuit which is formed and whose capacitance is charged by a silicon-controlled rectifier triggered by the engine. The resulting half-sine wave voltages across the load resistance are of -constant duration and are changed from a half-sine waveform to more triangular waves. Transistor circuits, at least one of which is biased by a voltage representing a number of engine operating conditions, convert the triangular waves into square wave voltages having a constant amplitude and a duration corresponding to the engine operating conditions. The resulting square waves or pulses are applied to solenoid injector valves to open them synchronously with the engine for required periods of time to supply the needed amounts of fuel.

ENGINE /26 VARIABLES PATENTEUUBT12I97I SHEET 2 UF 3 INVENTOR RICHARD B. BEISHIR WM ('M/ ATTORNEY PATENTED nm 1 2 I97! SHEET 3 BF 3 INVENTOR RICHARD B. BEISHIR WNW ATTORNEY ELECTRONIC FUEL INJECTION CONTROL CIRCUIT BACKGROUND OF THE INVENTION Electronically controlled fuel injection systems have been proposed for spark ignition internal combustion engines utilizing solenoid valve injectors, which are opened at engine speed for a period varying in accordance with engine operating requirements. In order to practical for widespread use for long periods without adjustment or repair, the control circuit must be simple and stable. It is, accordingly, an object of the invention to provide simple inexpensive transistor circuits for properly controlling the fuel injection valves of a spark internal combustion engine.

SUMMARY OF THE INVENTION Control and metering circuits are provided for fuel injection system valves for automobiles. A capacitance in series with inductance and resistance is charged by a voltage source. A silicon controlled rectifier connected between the positive side of the capacitance and ground is triggered by the engine to discharge the capacitance into the resonant circuit so formed fora predetermined number of times during each engine revolution, producing half-sine waves across the load re-v sistance having a fixed duration. Wave shaping circuits transform the half-sine waves into waves having a more triangular -form. In one embodiment of the invention a field effect transistor shunts the resonant circuit. The transistor is biased in accordance with the engine operating variables to control the damping factor of the resonant circuit so that the amplitude of the half-sine voltage waves will vary with the engine requirements. A biased transistor converts the triangular waves into square waves of varying duration, and the square waves are applied to solenoid fuel injection valves for periods corresponding to the engine requirements. In another circuit embodiment, the engine variables control the bias of a transistor on which constant-amplitude, half-sine voltage waves are impressed to produce the variable duration square waves. In still another embodiment of the invention, differentiating and squaring circuits are utilized and their outputs are combined to produce substantially triangular voltage waves on the input of a variably biased comparator circuit, which consequently yields square waves of variable duration for the injection valves.

BRIEF DESCRIPTION OF THE DRAWING The accompanying drawing consists of the following figures:

FIG. 1 is a circuit diagram of one embodiment of the invention.

FIG. 2 is a diagram of another embodiment.

FIG. 3 is a diagram of a third embodiment of the'invention.

FIG. 4 is a plurality of charts applicable to the circuit of FIG. 2.

FIG. 5 shows charts applicable to the circuit of FIG. 3.

FIG. 6 shows charts applicable to the circuit of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, the automobile fuel injector circuit of FIG. I is connected to a voltage source from the automobile via terminals 10 and 11. The general purpose of the circuit is to energize one or more solenoid operated fuel injector valves. Terminal 10 is connected through resistor 12 to a circuit including capacitor 14 and inductance l6, and resistor 18. The series connection of field effect transistor 20 and capacitor 22 shunts the series connection of inductance l5 and resistor 18, The gate field effect transistor is energized from terminal 10 via resistor 24. The gate of the field effect transistor is connected to computer 26, which generates a control voltage representing the automobile engine operating variables, such as manifold vacuum, engine temperature, barometric pressure, acceleration, etc. The magnitude of the signal impressed on the transistor gate by computer 26 determines the amount of damping imposed on resonant circuit l4, l6.

Capacitor 14 is discharged as part of the resonant circuit through silicon controlled rectifier (SCR) 28. The latter is fired by applying a triggering pulse to gate electrode 30 via terminal 32. The pulse may be produced by a switch closed periodically by the engine, or by coupling to the ignition circuit, so that a given number of pulses is generated during each engine cycle. THe discharging of the resonant circuit composed of capacitor 14, inductance '16, and load resistance 18 through SCR 28 produces a voltage pulse across resistor I8 approximating a half-sine wave. THeamplitude of the halfsine wave varies in accordance with the resistance of transistor 20, as indicated by the family of curves 83 of FIG. 6. The halfsine waves appearing at tenninal 34 are applied to buffer amplifiers 36, 38, which prevent mutual loading of odd harmonic trap circuits 40, 41 and 42, 43. Thesecircuits change the form of the voltage pulses to produce approximately triangular waves shown at 84 in FIG. 6, at terminal 44. Rectifier 46 is provided to short circuit any positive overshoots of the triangular waves, Amplifier 48 connects the triangular waves 84 to square wave output 85 when its bias is overcome by the input pulses, the output pulses to have a duration varying with the amplitude of the input pulses and being of nearly fixed amplitude.

It is common practice to provide a solenoid injector valve 50 for each cylinder and to switch the output of the control circuit to each solenoid in turn by means of an engine driven distributor 52, or to energize a plurality of solenoid valves simultaneously, as shown in U.S. Pat. No. 3, 240,191 and No. 3,412,718 respectively; and any of these or other modes of operation may be utilized.

It is evident from the above description that amplifier 48 produces square pulses of nearly fixed height and a duration which varies with the amplitude of the triangular pulses, which amplitude in turn varies the bias imposed on junction transistor 20 by analog computer 26 in response to the engine operational variables. Thus, solenoid valve 50 is energized and opened to feed fuel for a period determined by the engine variables. The embodiment of the invention shown in FIG. 2 utilizes a resonant circuit which is charged and discharged in the same manner as the circuit of FIG. I, and the same reference numerals are used for like parts in the two figures. Thus, the voltage source connected to terminals 10 and 11 charges the capacitance 14, through resistors 12 and I8 and inductance 16. A resonant circuit is periodically formed by firing SCR 28, by applying trigger pulses to terminal 32, which is connected to gate electrode 30. The charging rate of the capacitance 14 is preferably very rapid, so that no appreciable voltages develop across resistor 18, but in any event these voltages are positive and have no appreciable efiect on the following circuit elements. The discharge of capacitance l4 produces negative-going half-sine wave voltages of constant amplitude and time duration at terminal 34. These voltages are supplied through capacitor 62 to a conventional dil ferentiating circuit 64 to produce voltage pulses 66 (FIG. 4) at terminal 68. The pulses at terminal 34 are also applied to overdriven amplifier 70, which produces squared pulses indicated ideally at 72. Pulses 66 and 72 are applied additively to the input of comparator 74.

Analog computer 26 produces an output which is a function of the engine operating variables, and the output of computer 26 biases comparator 74 to a required level, three values 81, B2 and B3 of which are indicated in FIG. 4. The addition of pulses 66 and 72 yield pulses 76, which may exceed the bias on comparator 74 for a period determined by the value of the bias. As a result, the comparator produces square pulses 78 having a width varying as a function of the bias; and hence, also, as a function of the engine variables. The square pulses from comparator 74 are impressed on output amplifier 80. which supplies square pulses of variable width to the solenoids of valves 50, one of which is illustrated in FIG. 2. Thus, valves 50 are opened during each engine cycle for periods which permit the flow of the required amount of fuel. FIG. 3 shows a variation of the circuit of FIGS. 1 and 2, utilizing many like elements having the same reference numerals. Here, again, the voltage source is connected to terminals and 11. Resonant capacitance l4 and inductance 16 are connected in series with resistor 12 and load resistor 18, and silicon controlled rectifier 28 is connected between resistor 12 and terminal ll. Rectifier 28 is triggered in the same manner as it is in FIGS. 1 and 2. Half-sine wave voltage pulses appearing at terminal 34 are amplified by buffer amplifiers 36, 38, and these pulses are modified by odd harmonic trap circuits 40, 41 and 42, 43 to produce more nearly triangular voltage pulses at terminal 44. Diode clipper 46 removes positive voltage swings at terminal 44. The triangular pulses at terminal 44 are impressed on the input of comparator circuit 74, which is similar to that of FIG. 2, and is biased by analog computer 26 in the same manner. The output of comparator 74 is a nominally square wave of variable duration, which is amplified by output amplifier 80 and then impressed on the solenoid of one or more solenoid injector valves 50.

FIG. 5 indicates schematically the manner in which the duration of the square waves is varied by comparator 74. The nominally triangular pulses 82 impressed on comparator 74 have a fixed amplitude and fixed width. Computer 26 produces cutoff bias voltages B1, B2, B3, B4, for example, in accordance with the engine operating conditions, and im presses the bias voltages on comparator 74. The comparator conducts during the period when the triangular wave exceeds the cutoff bias voltage. Thus, for the high bias voltage B11, comparator 74 yields the narrow square wave 84 shown in solid lines in FIG. 5. For lower bias voltages B2, B3, B4, the progressively wider square wave pulses shown in dashed lines 86 are produced. The wider pulses hold the solenoid valves 50 open for a longer time and permit a greater amount of fuel to be supplied to the engine. Thus, the amount of fuel required under various operating conditions is provided.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A fuel injection system for an internal combustion spark engine, comprising a circuit having a resistor and inductor in series with a capacitor which is charged by a source of voltage; electronic switching means responsive to engine speed connected to said circuit for short circuiting said circuit and thereby rendering it resonant and discharging the same a predetermined number of times during each engine cycle; means connected to said resonant circuit for deriving during each discharge thereof a substantially sinusoidal half-wave voltage therefrom having a fixed period; means for peaking said sinusoidal voltage waves; means for injecting fuel into the cylinders of the engine; and means for activating said fuel injecting means in response to each peaked half wavc for a period having a variable duration determined by the engincoperating conditions.

2. A system according to claim 1, wherein the means for activating the fuel-injecting means includes circuit means for producing square waves having a duration determined by the engine operating conditions.

3. A system according to claim I, wherein said means for producing the peaked waves includes a differentiating circuit producing a bidirectional, generally triangular wave and square wave generating circuit connected in parallel with said differentiating circuit and having their outputs superimposed to form a generally triangular wave having only one polarity.

4. A system according to claim 1, including means for damping said resonant circuit by an amount varying according to the engine operating conditions.

5. A system according to claim 4, wherein said damping means includes a field effect transistor effectively connected in parallel with a portion of the resonant circuit, means for biasing said transistor in accordance with the engine-operating conditions.

6. A system according to claim 1, including means for varying the amplitude of said sinusoidal half-waves in accordance with the engine-operating conditions. 

1. A fuel injection system for an internal combustion spark engine, comprising a circuit having a resistor and inductor in series with a capacitor which is charged by a source of voltage; electronic switching means responsive to engine speed connected to said circuit for short circuiting said circuit and thereby rendering it resonant and discharging the same a predeTermined number of times during each engine cycle; means connected to said resonant circuit for deriving during each discharge thereof a substantially sinusoidal half-wave voltage therefrom having a fixed period; means for peaking said sinusoidal voltage waves; means for injecting fuel into the cylinders of the engine; and means for activating said fuel injecting means in response to each peaked half-wave for a period having a variable duration determined by the engine-operating conditions.
 2. A system according to claim 1, wherein the means for activating the fuel-injecting means includes circuit means for producing square waves having a duration determined by the engine operating conditions.
 3. A system according to claim 1, wherein said means for producing the peaked waves includes a differentiating circuit producing a bidirectional, generally triangular wave and square wave generating circuit connected in parallel with said differentiating circuit and having their outputs superimposed to form a generally triangular wave having only one polarity.
 4. A system according to claim 1, including means for damping said resonant circuit by an amount varying according to the engine operating conditions.
 5. A system according to claim 4, wherein said damping means includes a field effect transistor effectively connected in parallel with a portion of the resonant circuit, means for biasing said transistor in accordance with the engine-operating conditions.
 6. A system according to claim 1, including means for varying the amplitude of said sinusoidal half-waves in accordance with the engine-operating conditions. 